1. Field of the Invention
The present invention relates to a touch sensor type liquid crystal display equipped with a touch sensor function on a liquid crystal display panel, and more particularly to a liquid crystal display with a resistive membrane touch sensor.
2. Description of the Related Art
Resistive touch membrane sensors are employed to provide a way to input or select information displayed on a display device. Referring to FIG. 13, an example of a conventional resistive membrane touch sensor type liquid crystal display is shown, which was disclosed in Japanese Patent Laid-Open Hei 7 (1995)-84705. In the present specification, a touch sensor type liquid crystal display means one having a touch sensor function added to a liquid crystal display panel, whatever mode may be employed.
As shown in FIG. 13, this touch sensor type liquid crystal display 1 includes a touch sensor panel 3 laminated on a liquid crystal display panel 2. The liquid crystal display panel 2 has a structure, which is made by laminating an upper polarizing plate 12, a color filter substrate 13 made of glass, an array substrate 14 made of glass, a lower polarizing plate 15 and a backlight unit 16 from the upper part of the drawing. Peripheral parts of the color filter substrate 13 and the array substrate 14 are sealed with a sealing material 17, and a liquid crystal material is sealed in a space to form a liquid crystal layer 18. Though not shown in FIG. 13, the liquid crystal layer 18 includes spacers for controlling a gap between the color filter substrate 13 and the array substrate 14: typically, a number of spherical members called beads are dispersed in the pixel region. Various improvements have been made for spherical spacers. For example, Japanese Patent Laid-Open Hei 5(1993)-80343 disclosed spherical spacers, which are capable of reducing non-uniformity of the gap and are not foamed at a low temperature.
The touch sensor panel 3 is laminated on the liquid crystal display panel 2 by an adhesive tape 6. The touch sensor panel 3 includes a fixed electrode plate 4 made of glass, and a movable electrode plate 5 made of glass and arranged opposite the fixed electrode plate 4 at a specified interval by using the adhesive tape 6. The fixed electrode plate 4 includes a transparent conductive film 7 made of ITO (indium tin oxide), SnO2 or the like formed on the surface, and the movable electrode plate 5 includes a similar transparent conductive film 8. Grids 9 are disposed between the fixed and movable electrode plates 4 and 5 to prevent unexpected contact therebetween.
In both ends of the fixed and movable electrode plates 4 and 5, electrode terminals 10 are pasted by silver or the like in directions orthogonal to each other. Wires of the electrode terminals 10 formed on the fixed and movable electrode plates 4 and 5 are collected at one place and connected to a flexible substrate 11.
The touch sensor type liquid crystal display became popular remarkably fast. Now, these type of displays can be seen in many places, for example, bank ATMs, ticket machines at train stations, and so on. Use of the touch sensor type liquid crystal display is not limited to the installed type equipment such as ATM or the like, but application thereof has expanded to a portable or mobile equipment.
One of the tasks regarding the mobile equipment is a reduction in weight. This task is also required for the touch sensor type liquid crystal display. One problem for the weight reduction has been the use of a glass substrate, which forms a touch sensor panel.
At present, a mainstream type of the touch sensor panel 3 is one, which includes the fixed electrode plate 4 made of glass, and the movable electrode plate 5 made of a plastic film such as PET (polyethylene terephthalate) or the like. However, even for the type having the movable electrode plate 5 made of a plastic film, a sufficient reduction cannot be made in weight because the fixed electrode plate 4 is made of glass. Consequently, although there are latent demands for fixing the touch sensor panel in a notebook personal computer using, for instance, a liquid crystal display panel of 13.3 type, practical use thereof has not yet been realized.
As a lighter and thinner touch sensor panel, types having both fixed and movable electrode plates made of plastic films have been known. Widely used among these types is one having a thickness of the plastic film set in a range of 10 μm to 3 mm, especially in a range of 100 μm to 500 μm. However, it has been pointed out that the touch sensor type liquid crystal display constructed by laminating the touch sensor panel of this type on the liquid crystal display panel cannot endure long-time use. This is because low rigidity of the touch sensor panel causes a pressing force at the time of touching to be applied to the liquid crystal display panel, and an image characteristic thereof is adversely affected.
The touch sensor type liquid crystal display described in above-mentioned Japanese Patent Laid-Open Hei 7 (1995)-84705 is constructed by eliminating the fixed electrode plate of the touch sensor panel, and providing the function thereof using the color filer substrate of the liquid crystal display panel instead. In the case of this touch sensor type liquid crystal display, a problem similar to the above may occur if the movable electrode plate is made of a plastic film.
It is an object of the present invention to provide a touch sensor type liquid crystal display, which can endure long-time use is reduced in weight. It is another object of the invention to provide a liquid crystal display panel suitable for used as a touch sensor type liquid crystal display.